This invention relates generally to a fuel pump and more particularly to a turbine type fuel pump and method for calibrating the same.
Electric motor driven turbine type fuel pumps are customarily used in automotive engine fuel delivery systems and the like. These pumps typically include a housing adapted to be immersed in a fuel supply tank with an inlet for drawing liquid fuel from the surrounding tank and an outlet for supplying fuel under pressure to the engine. The electric motor drives a pump impeller with an array of circumferentially spaced vanes about the periphery of the impeller. An arcuate pumping channel, with an inlet port and an outlet port at opposed ends surrounds the impeller periphery for developing fuel pressure through a vortex-like action on liquid fuel in pockets formed by the impeller vanes and the surrounding channel. One example of a fuel pump of this type is illustrated in U.S. Pat. No. 5,257,916, and two other examples are U.S. Pat. No. 6,227,819 B1 and U.S. Pat. No. 6,068,456, all three being incorporated herein by reference.
Typically, the impeller type turbine fuel pumps have guide rings which strip the fuel from the impeller vanes thereby diverting the fuel through an outlet port. The channel is carried radially between the impeller and a substantial portion or trailing segment of the guide ring. A smaller portion or stripper segment of the guide ring is disposed circumferentially between the inlet and outlet ports and is closely orientated to the impeller for stripping the moving vanes of high pressure fuel, thereby preventing the fuel at the outlet port from bypassing the fuel pump outlet and exiting back into the low pressure inlet port.
Despite significant improvements in the design and construction of turbine type fuel pumps, they are generally very inefficient with an efficiency of generally between about 20% to 40%, and when combined with a typical electric motor having an efficiency of about 45% to 60%, the fuel pumps have an overall efficiency of between about 15% to 30%. Any fuel bypass from the high pressure outlet port back into the low pressure inlet port will contribute to this inefficiency. Moreover, under heated fuel conditions, the efficiency is significantly impaired even further.
A turbine fuel pump assembly draws fuel from a reservoir and supplies that fuel to a combustion engine. The assembly includes an electric motor which drives a fuel pump, all of which is supported in a sleeve. The fuel pump has a guide ring which has a stripper segment for stripping or shearing fuel off of the vanes of an impeller and redirecting the fuel through an outlet port of the fuel pump. The turbine fuel pump assembly can be easily calibrated for improved pumping efficiency via a calibration ring tool which plastically deforms the sleeve externally by producing a dimple upon the sleeve and a corresponding interior protuberance which bears radially inward against a trailing segment of the guide ring to calibrate or move the cantilevered stripper segment against the impeller to a point or location where fuel flow through the pump is optimized.
The impeller is mounted rotatably between an upper and lower cap of the housing. The guide ring which circumferentially surrounds the impeller is also disposed between the upper and lower caps but is held stationary with respect to the housing. An outward side of the guide ring faces the surrounding sleeve so that a protuberance disposed directly between the outward side of the guide ring and the surrounding sleeve biases the cantilevered stripper segment toward the impeller vanes for improved shearing of fuel off the rotating impeller.
Preferably, the stripper segment of the guide ring is engaged unitarily between an impact segment which partially defines a high pressure fuel outlet port, and a trailing segment which extends circumferentially beyond a low pressure fuel inlet port of the housing. Preferably, the guide ring is split by a slit defined circumferentially between the impact segment and distal end of the trailing segment. The stripper segment is thus cantilevered with respect to the trailing segment so that the protuberance, created during the calibration process, pushes against the trailing segment at a location near the inlet port and the stripper segment, causing the stripper segment to cantilever or move radially inward against the impeller. Preferably, the protuberance is unitary to and projects radially inward from the sleeve.
Objects, features and advantages of this invention include a turbine fuel pump assembly that has a significantly improved efficiency and a method of calibration utilizing a novel calibration ring tool to gain such improved efficiencies. The invention may be readily incorporated into and/or performed on existing fuel pump designs, increases fuel output flow at cold and hot fuel temperatures, is of relatively simple design and economical manufacture and assembly and in service has a significantly increased useful life.